Somali Butterflyfish

Almost nobody diving the 🌊 Red Sea will see this one. Its range reaches the sea only at the far southern end, around the Farasan Islands and the Yemeni coast, and the whole northern half where most diving happens is outside it. Add a preferred depth of 7 to 75 m and a taste for the rubble at the foot of slopes rather than the bright coral above, and the result is a fish better known from East Africa than from here.

It is easy to name if you do find it. The body is split along a diagonal: dark gray-black over the top half, clean white below, with no gradient between them. A curved yellow line follows the rear edge of the gill cover, a black bar runs through the eye, the upper lip is black, and the fins are yellow. No other butterflyfish in this sea is two-tone in that way.

It works ground the rest of the family has little use for. Coral scree and open bottom at the base of a slope hold worms, small crustaceans and scattered polyps, and this fish takes all of them, which is presumably why it can live where coral cover is thin. Its measured trophic level is low even by butterflyfish standards.

Singles and pairs are both usual, out over open seafloor rather than tucked into a colony. Like the rest of the family it spawns into the water column and gives its eggs nothing afterward.

Lambert Playfair, a Scottish naturalist and British consul at Zanzibar, described it in 1867 from a specimen taken there. The common name points at 🇸🇴 Somalia, but the Somali coast is only the middle of a range that runs from the southern 🌊 Red Sea down to Zanzibar and out to Aldabra (🇸🇨 Seychelles) and the 🇸🇨 Seychelles.